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Why 1K boundary is used in AHB Bus ??

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uditkumar1983

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ahb 1k boundary

Hi
My doubt is that in AMBA-AHB there is 1K Boundary , So what is the advantages of this 1K boundary??
 

jackson_peng

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burst 1k boundary

as i remembered, the memory map boundary is 4k, with 12 bits.
it saves the logic overhead in AHB Bus Controller, who only have to decode first 20 bits in address bus to select a slave.
 

uditkumar1983

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burst must not cross 1kb address boundary

Hi jackson,
I did't understood "memory map boundary is 4k ", through which means u r taking about ...
But in case of AMBA-AHB if any master is trying to cross 1K address boundary then its not allowded ,then it will go into break state.... So in AMBA-AHB it is 1K only.....For ref u can see AMBA Specification (Rev 2.0)
Thanks in advance.....
 

archillios

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ahb 4k boundary

hi,
as i know, AHB Slave space should not less than 1KB, the reason lies on simple decoder design. You need only decode 20-bit address signals, not full 32-bit.
If there has no constraints about burst address, when one AHB burst transfer is going, it may go across 1KB boundary, run into another slave memory!
For this reason, AHB spec. constraints that one incrementing transfer should not cross 1KB boudary.
 

uditkumar1983

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ahb why 1kb address boundary

Hi ,
Now i got it ...
Thanks ...
 

learnbydo

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ahb burst 1 kb boundary

one purpose is to avoid across two slaves in one transfer
 

uditkumar1983

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ahb 1k

Hi learnbydo,
I did't got this , Please explain it ..
 

nikhils.vlsi

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amba ahb 1k boundary

uditkumar1983 said:
Hi learnbydo,
I did't got this , Please explain it ..

may be this may help you

1 kilobyte is the smallest area an AHB slave may occupy in the memory map. Therefore,if a burst did cross a 1 kilobyte boundary, the access could start accessing one slave at the beginning of the burst and then switch to another on the boundary, which must not happen for the above reason.

The 1 kilobyte boundary has been chosen as it is large enough to allow reasonable length bursts, but small enough that peripherals can be aligned to the 1 kilobyte boundary without using up too much of the available memory map.
 

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